London, 1893. The Order of Apollo, investigator of mysterious events for the Crown, has been uncovering artefacts and refugees from another world, smuggled through boundaries that seem to be thinning. A breach would mean disastrous consequences for the entire universe. Meanwhile, rumours abound of an enemy the Order thought long-since dead, alive and gathering followers. Colonel John Hardwick, an embittered veteran of Apollo, is forced to join the fight again, with his former friend Captain Jim Denny and mysterious adventuress Marie Furnival. But facing this new threat brings them to dark secrets that implicate whole nations and threaten the very fabric of reality.